The CAS Registry Mumber 4252-57-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,2,5 and 2 respectively; the second part has 2 digits, 5 and 7 respectively. Calculate Digit Verification of CAS Registry Number 4252-57: (6*4)+(5*2)+(4*5)+(3*2)+(2*5)+(1*7)=77 77 % 10 = 7 So 4252-57-7 is a valid CAS Registry Number.